Chullin, Chapter 3, Mishnah 7. The closing mishnayot of this chapter move away from the treifot and take up the simanim, the identifying signs, by which we recognize the permitted species. Our mishnah presents the signs of a kosher locust and the signs of a kosher fish.
The Four Signs of a Kosher Locust
The mishnah begins: "uvachagavim" - and with regard to locusts. A locust that bears the following four signs is kosher.
- "Kol sheyesh lo arba raglayim" - it has four legs, two on either side of its body.
- "Ve'arba kenafayim" - it has four wings, two on either side of its body.
- "Vekarsulayim" - it has two long jumping legs.
- "Uchenafav chofin et rubo" - its wings cover the greater part of its body.
A locust possessing all four of these is a kosher locust.
Which Signs Come From the Pesukim
Two of these signs are spelled out plainly in the Torah in the passage that permits certain locusts. The pasuk describes the creature as "haholech al arba" - one that moves about upon four, and as one "asher lo chera'ayim mima'al leraglav" - possessing jumping thighs set higher up than its ordinary feet, "lenater bahen al ha'aretz" - by means of which it springs over the ground.
Thus the Torah itself supplies two of the simanim. The other two, namely the four wings and the demand that those wings sheathe the majority of the creature's frame, reach us through the teaching of the Chachamim.
Rabbi Yose's Fifth Requirement
"Rabbi Yose omer: ushmo chagav" - Rabbi Yose requires a fifth condition: the creature has to belong to the chagav family, carrying that very name. He too anchors his condition in the pesukim: the species has to be one that people recognize by the name chagav. The physical simanim alone do not settle the matter; the name must fit as well.
The Signs of a Kosher Fish
"Uvadagim" - turning now to fish, a fish becomes permitted through two simanim: "kol sheyesh lo senapir vekaskeset" - whichever fish possesses a senapir together with a kaskeset. Note that the Torah writes each term in the singular.
Scripture states this directly: "Et zeh tochlu mikol asher bamayim" - of everything in the water, this is what you may eat, "kol asher lo senapir vekaskeset" - whatever possesses a fin along with a scale. Since the words are singular, one solitary fin together with one solitary scale already renders the fish permitted.
Rabbi Yehuda's View
"Rabbi Yehuda omer: shenei kaskasin usenapir echad" - Rabbi Yehuda requires a pair of scales alongside a single fin. He understands "kaskeset" as a plural form built on the singular "kaskas," so that the Torah is in fact demanding two scales before the fish may be eaten.
Telling a Fin From a Scale
A fin and a scale look remarkably alike: each is a fold-like protrusion growing out of the creature's skin. For that reason the mishnah proceeds to teach how to tell the one from the other, so that a person can establish whether both simanim are present and the fish is permitted.
"Ve'elu hen kaskasin" - these are the scales: "hakevu'in bo" - those that are fixed to its body. They are attached and do not move, and the fish does not use them to glide through the water.
"Usenapirin" - and the fins are "haporeach bahen" - those with which the fish propels itself and swims through the water.